Improvement in instrument tor describing spiral lines



dtitrd gata-ien LEWIS W. TRUESDELL,

or-ownco, New YORK.

' Letters'Pa-tent No.1.97,571, dated Decembefr, 186i);` fmtedated November 30, 1869.

IMPROVEMENT IN INSTRUMENT FOR DESGRIBING- SPIRAL LINES.

Tha Schedule referred to in these Letters Patent and making part of the same.

To all whom it may concern Be it known that I, Lewis W. TRUEsDnLL, of

Owego, in the county of Tioga, and State of New York, have invented anew and improved Instrument for the Use oi'Draughtsmen and Engineers, in Drawing ing the instrument, and the centre pivot on which the instrument turns.

Figure 3 is an elevation ofthe traverse-wheel E. Figure 4, a vertical transverse section of wheel E.

To enable others skilled in the art, or that to which it is most nearly allied, to make and use my invention, I-will describe its construction and operation.

In the accompanying drawings- A is a fixed arm, attached to the drawing-boar`d, by which the instrument is held in position while being operated.

B is a crank on the top of the centre pivotU, which passes through the arm A.

Attached to the bottom of the pivot O, is a clamp, It', partially surrounding the horizontal bar D.

This bar may be moved through theclamp k, from end to end, and fixed in any desired position by turning the crank, which, by means of ,a screw, forces down a stem, f, lig. 2, upon the bar Dy Attached to the ends of the bar D are two vertical rods e e, fig. 1, supporting, at their lower ends, the screw-shaft F.

On the screw are three separate parts, viz, the traverse-wheel E, a sleeve carrying the pencibpoint b, and the collar o, which engages in the screw-thread.

The traverse-wheel is composed of a metal ring, J, with its periphery recessed to receive a rubber band, E', while Within it, and litt-ed so as to turn freely, is a narrow ring, through opposite s ides of which pass two screws t t', tig. 4.

These screws hold in their points a short sleeve or tube, n, through which passes the screw-shaft F, in the centre of the wheel.

The ring through which the screws tt pass is kept in place by a bushing, S, g. 4, screwed up toit in the ring J, but allowing the inner ring to turn freely in the outer one.

The inner ring has a narrow plate firmly attached to it, whichl passes out to the side of the traversewheel, which is then formed in the shape of a section of a circle, m, the periphery of which is outward, and the screws t i, in the rng,are in the centre.

The tube n, in the centre of the wheel, and which is held in place on the points of the screws t' t', is provided with a small piece, which passes out under the plate fm, and turns at a right angle across its circular edge, so that a set-screw, r, in the extension of the tube n, when turned up, will come in contact with the circular edge ofthe plate m.

rlhe sleeve on the screw-shaft F, carrying the'pencil b, has a screw on each end, by which it may be attached either to the tube u in the traverse-wheel, or

to the ring o on thej screw-shaft.

One end of the tube a, on the screw-shaft F, has a slot, c, and the traverse-wheel is also provided with a narrow groove on the same side, and when the traverse-wheel is moved to the end oi' the instrument, a thin plate, d, on the shaft F, enters the,slot in the tube and traverse-wheel, which causes bothto revolve together. V

The socket holding to press the pencil down upon the paper to be drawn upon.

follows:

The instrument is suspended in the arm A by the vertical pivot G; the traverse-wheel is moved to the end of the shaft F, and slipped upon the plate d the bar Dis placed in the clamp lt, so that the wheel Il shallv be at the proper distance fromthe centre pivot O; the pencil placed under the centre pivot; the collar o turned up to the sleeve carrying the pencil, and screwed on. The instrument is then sweptround by turning the crank B. The rubber band E, on thc traverse-wheel, running on the drawing-board or paper, makes sufticient friction to revolve the wheel 'and shaft F, and the screw causes the pencil to recede from the centre as it revolves around the pivot C.

It will be seen that the distance from the traversewheel to the centre pivot will determine the number of revolutions ofthe screw-shaft, and consequently the pitch of the spiral to be drawn; and the bar D must be so placed in the clamp k, that the spiral shall be of' the pitch desired.

In drawing concentric lines oi' varying pitch, the screw-thread ou the shaft Fis not used. The traversewheel is slipped oii from the plate d, the pencil-sleeve is screwed fast to the end ot' the tube n, and the collar o is detached from the pencil, and turned back out ot' the way. The set-screw ris loosened, and the traverse-wheel is turned on the pointed screws t i, so that it will stand at any desired angle with the shaft lll; The set-sercw r is turned against the edge of the plate m, to retain it in that position. The outer ring,C J of the-traverse-wheel now turns upon the inner one ;I this, with the tube n', which is attached to the pencil-carrier, being thereby prevented from turning.

Now if the instrument is swept round as before, the

the pencil has a spring inside,

In drawing spirals, the instrument is operated as y traverse-wheel and pencil being fre-e to slide on the shaft F, the variation of the traverse-wheel from a right angle withthe shaft F, will cause the traversewheel to recede from the centre or approaeh it this depending upon the direction the machine is turned, or the way the wheel is inclined on the shaft.

The pitch of the volute drawn is governed by the angle of the wheel upon the shaft F.

What I claim as my invention, and desre'to secure by Letters Patent, is-

1. The peculiar construction'of .the traverse-wheel E, with its outer ring, J, with rubber band thereon, the inner ring with its plate m, and screws holding the tube n, with its projecting arm and set-screw fr, or any arrangement of parts substantially Idie same as herein set forth and described.

2. In combination with the traverse-wheel E, the screw-shaft F, pencil-carrier b,v and ring o, when these several vparts are applied in a compound Spiro-volutograph for drawing concentric spiral lines, in the 'manner herein specified.

LEWIS W. TRUESDELL.

Witnesses H. A. BROOKS, J J. VAN KLEEGK. 

